Study on enhancement and mechanism of K2SO4 in CMP slurries for copper film polishing removal effect

The efficient copper removal of the in the multi-layer copper interconnect copper film chemical mechanical planarization (CMP) process is one of the important indicators for high production efficiency of integrated circuit process. The chemical corrosiveness of polishing slurries to copper is the key factor affecting the copper removal rate. Since the copper polishing slurries are relied too much on the synergistic effect of complexing agent and oxidant for the copper chemical dissolution to achieve efficient removal of copper film, the planarization and corrosion of copper CMP cannot be well improved. In this paper, it was found that adding potassium sulfate (K2SO4) in polishing slurries can improve the copper removal effect of CMP. In this paper, the mechanism of the effect enhancement of K2SO4 was explored with series of characterization experiments. Firstly, the influence of K2SO4 on the increase of electrochemical corrosion degree of copper electrode was studied by electrochemical method. Secondly, based on X-ray photoelectron spectroscopy (XPS) and laser scanning confocal microscope (LSCM), it was determined that the copper surface oxide formation increased after electrochemical corrosion caused by K2SO4. Finally, the efficiency of copper polishing removal of K2SO4 in polishing slurries was verified by CMP experiments, and the dynamic oxidation enhancement mechanism of K2SO4 in polishing slurries for CMP copper removal was analyzed.